1. Field of the Invention
The present invention relates to a timepiece equipped with a calendar mechanism including a first date indicator for displaying the ones digit of the date and a second date indicator for displaying the tens digit of the date. More particularly, the present invention relates to a timepiece equipped with a calendar mechanism and designed such that the center axis of rotation of the time display wheels is located inside the center hole in a program gear.
2. Description of the Prior Art
(1) Description of Terminology
Generally, the mechanical body of a timepiece including the driver portion is referred to as the “movement”. A dial and hands are attached to the movement and put into a timepiece case, forming a completed product. This state is referred to as the “completed” state of the timepiece. A bottom plate or movement plate forms the base plate of the timepiece. The side of the bottom plate which faces the timepiece case glass or on the side of the dial is referred to as the “rear side”, “glass side”, or “dial side” of the movement. The other side of the bottom plate which faces the rear cover of the timepiece case (i.e., which faces away from the dial) is referred to as the “front side” or “rear cover side” of the movement. A train wheel incorporated on the “front side” of the movement is referred to as the “front train wheel”. A train wheel incorporated on the “rear side” of the movement is referred to as the “rear train wheel”. Generally, “12 o'clock side” indicates a side of an analog timepiece on which a scale mark corresponding to the 12 o'clock on a dial is disposed. “12 o'clock direction” indicates a direction directed toward the “12 o'clock side” of an analog timepiece from the center of rotation of hands or fingers. “3 o'clock side” indicates a side of an analog timepiece on which a scale mark corresponding to the 3 o'clock on the dial is disposed. “3 o'clock direction” indicates a direction directed from the center of rotation of fingers or hands of an analog timepiece toward the “3 o'clock side”. Furthermore, “6 o'clock side” indicates a side of an analog timepiece on which a scale mark corresponding to the 6 o'clock on the dial is disposed. “6 o'clock direction” indicates a direction directed from the center of rotation of fingers or hands of an analog timepiece toward the “6 o'clock side”. In addition, “9 o'clock side” indicates a side of an analog timepiece on which a scale mark corresponding to the 9 o'clock on the dial is disposed. “9 o'clock direction” indicates a direction directed from the center of rotation of fingers or hands of an analog timepiece toward the “9 o'clock side”. Additionally, sides on which other scale marks on the dial such as “2 o'clock direction” and “2 o'clock side” are disposed may be indicated.
(2) Prior Art Timepieces with Calendar Mechanism
The structure of the prior art timepiece equipped with a calendar mechanism including a first date indicator for displaying the ones digit of the date and a second date indicator for displaying the tens digit of the date is described below.
(2-1) Calendar Mechanism-Equipped Timepiece of the Prior Art First Type
Referring to FIG. 25, a calendar mechanism-equipped timepiece of the prior art first type has two date indicators 822 and 824 which overlap each other at least partially. The first date indicator 822 provides a display of the ones digit of the date, while the second date indicator 824 provides a display of the tens digit of the date. A drive mechanism includes a 24-hour wheel 820 rotated once every 24 hours by rotation of an hour wheel 816, an operating lever 844 operated by rotation of the 24-hour wheel 820, other gears for control and the like. A program wheel 850 is rotated by operation of the operating lever 844. A first date indicator driving wheel 852 rotates the first date indicator 822. A second date indicator driving wheel 854 rotates the second date indicator 824. Rotation of the first date indicator 822 is corrected or regulated by a first date indicator jumper 862. Rotation of the second date indicator 824 is corrected or regulated by a second date indicator jumper 864 (for example, see EP 1,070,996 A1).
(2-2) Calendar Mechanism-Equipped Timepiece of the Prior Art Second Type
Referring to FIG. 26, a calendar mechanism-equipped timepiece of the prior art second type has an ones disc 932 for displaying the “ones” digit of the date and a tens disc 931 for displaying the “tens” digit of the date. An ones pinion 933 is fixedly mounted to the ones disc 932. An ones jumper 936 maintains the angular position of the ones pinion 933. A tens pinion 934 is fixedly mounted to the tens disc 931. A tens jumper 940 maintains the angular position of the tens pinion 934. The ones pinion 933 is in mesh with the upper half of the tooth row of a date gear 908. The hooks of a drive device 906 are in mesh with the tooth row of the date gear 908, thus advancing the teeth of the date gear 908 one pitch each day. The tens pinion 934 is driven one pitch at a time by an intermediate movable part 937. The intermediate movable part 937 is driven one pitch at a time by the date gear 908 via an idle gear 938 (for example, see JP-A-2000-147148).
In the timepiece equipped with the prior art calendar mechanism of the first type, the drive mechanism for driving the first date indicator 822 and the second date indicator 824 includes the 24-hour wheel 820, the operating lever 844, other controlling gears, and so on. Therefore, the drive mechanism is complex in structure. There is the problem that the drive mechanism occupies a large area. Furthermore, in the timepiece equipped with the prior art calendar mechanism of the second type, the tens pinion 934 is driven by the date gear 908 via the intermediate movable part 937 and idle gear 938 and, therefore, the drive mechanism for driving the tens disc 931 is complex in structure. There is the problem that the drive mechanism occupies a large area. Furthermore, timepieces with the prior art calendar mechanism have problems that the drive mechanism is complex and that wide latitude is not offered in designing the calendar correction mechanism.